So far, it's going well. I have pumed every other day for a week an then stopped completely five days ago, while keeping track of weight an milk intake.
He has been growing well in the meantime, about 10 ounces a week, although his weight fluctuates from day to day, sometimes going sllightly down, which is a little bit scary. He always recovered so far, though.
If your baby is gaining that quickly you are fine as that is above average (nothing wrong with above average, but you certainly need not worry baby is not getting enough in that case.) Fluctuations in gain rate day to day or week to week are entirely 100% normal. Weight gain is just not something that would ever be precisely this or that per day or week. Additionally, be prepared for the fact that weight gain rate gets slower and slower as a baby ages. If babies kept gaining at the newborn rate they would be giants by the time they were 2. At this point you can stop weighing baby so much!

Also, I have been quite engorged all day yesterday, I hope my supply is not starting to go down too much.
Your milk production probably needs to ramp down somewhat, as you are making a little more than baby needs at this point. In that case milk production reducing is normal and expected. The more immediate issue with engorgement is that it might lead to plugs or even mastitis. If you are uncomfortable or getting hard, and baby will not nurse, fine to hand express a little milk for your own comfort. If hand expression is not working, you can pump but again, just enough to relieve the engorgement- this would be a time to pump "to comfort" and not to "empty" the breasts. That way you are getting milk out to help with your health and comfort, but not so much telling your body to make more. If you can get baby to nurse when you feel this way, that is usually the easiest and best option.

Might this be the time to offer him a bottle occasionally, to get him used to it, so that he does not refuse it later? He has not seen a bottle for a month exactly.
It sounds like things are going very well so yes, if you know that baby will need to take bottles at some point, fine to start the occasional practice bottle. To keep bottles from interfering in your and baby's breastfeeding progress, and to keep practice bottles from eating away your back to work stash, keep them small and infrequent. A couple times a week, an ounce at a time, is probably plenty for keeping baby in practice.
How about a pacifier? He started being quite cranky in the evening, refusing the breast and not sleeping for two hours or so, and it would perhaps help.
This is probably colic. If that is the case, if you can get baby to take a pacifier and it helps, fine. But don't count on it!

The caution to take with pacifiers is similar as with bottles. Just as ideally you want baby eating at the breast rather than with a bottle for most of the time, ideally you want baby comforting at the breast rather than with a pacifier most of the time. But parents do find pacifiers helpful when occasionally, baby will not nurse for comfort, and also when they cannot nurse baby like during a car ride. Basically you want to keep their use for a specific scenario(s) and as infrequent as possible. Again, also for your own comfort to relieve engorgement, encourage baby to nurse for comfort. Sometimes you can get baby settled first with the pacifier and then switch to nursing.